In recent years, development of components for optical communication has progressed according to the OIF (Optical Internet Working Forum) industrial group standard. The CMRR defined in the newest “Polarization Multiplexed Integrated Coherent Receiver Standard for 100 Gbps” by OIF (Non-Patent Document 1 described below) measures the output for each PD before connecting a balanced PD and specifies calculation by a prescribed formula.
While, in the coherent measurement technology forum, Keysight (formerly Agilent) Co. recognizes the need for CMRR versus frequency characteristic measurement, as yet it has not been possible to provide any specific measurement solution (refer to Non-Patent Document 2 described below).
International Publication WO2013-057967 (Patent Document 1 described below) is not related to measurement technique, but relates to automatic adjustment of the gain of a differential type transimpedance amp (TIA) at the stage after a balanced PD, and to an optical receiver whose CMRR is excellent.